Automatic wheel dresser



March 5, 1963 E. A. THOMPSON 3,079,906

AUTOMATIC WHEEL DRESSER Filed Feb. 5. 1960 6 Sheets-Sheet 1 INVENTOR.

EARL ATHOM PSON @AQZTM March 5, 1963 E. A. THOMPSON AUTOMATIC WHEEL DRESSER 6 Sheets-Sheet 2 Filed Feb. 3, 1960 INVENTOR. EARL. ATHOMPSON ATTORNEY March 5, 1963 E. A. THOMPSON 3,079,906

AUTOMATIC WHEEL DRESSER Filed Feb. 5. 1960 6 Sheets-Sheet 3 '-lll INVENTOR. EA EZLATHOMPSON A TTORNE) March 5, 1963 E. A. THOMPSON 3,079,906

AUTOMATIC WHEEL DRESSER Filed Feb. 3. 1960 6 Sheets-Sheet 4 IN V EN TOR.

EA BL ATHOMPSON A TTOR/VEV March 5, 1963 E. A. THOMPSON AUTOMATIC WHEEL DRESSER 6 Sheets-Sheet 5 Filed Feb. 3. 1960 k INVENTOR.

" EARLATHOMPSON March 5, 1963 E. A. THOMPSON AUTOMATIC WHEEL DRESSER 6 Sheets-Sheet 6 Filed Feb. 5, 1960 INVENTOR. I

United States Patent 6 35079366 AUTOFVIAFIIC WK-REL DREER H Earl A. Thompson, Ferndale, Mich. (13GO 'Hilton Road, Ferndaie Sta, Detroit 20, Mich.) Filed Feb. 3, 1966, Ser. No. 6,418 3 Claims. (Cl."125-11) 'Ihis'invention relatesto automatic re-dressing oire t'rueing mechanism for'agrinding'wheel, and more perticul-arly to'a dressing'unit and aremotely positionable power and control unit therefor, both of'which can readily be incorporated'in existing grindin'g'machines.

In the past, the dressing or trueing tool was mounted on suitable compound slide rests so that it could be me nipulated across the face of the Wh'eelb'y manually controlled'devices. This involved the grinding machineoperators shutting'down the workpiece feeding apparatus, usually walking around the'entire grinder to have access to the dressingtooland its controls, operating the dressing tool-by means of its' controls until the' Wheel face was satisfactorily redressed, and then coming backaroun'd the grinder and starting up theworkpiece feeding apparatus and letting it-run until a certain number of workpieces hadbeen'treated by the wheel; at'wh-ich' time the wheel again needed dressing and the entire procedure was started over. Aside from being inefiicient, this process resulted in inaccurate dressing; The worker who controlled the dressing t-o'ol had to tell-by ear and by feel at what speed thetool had. to be moved across the face of the wheel to obtain the particular wheel surface needed forthe type of workpiece being treated. The exact'surfac'e needed could not'beobtainedby this hit-and miss method every time, which'resulted variations 'in the quality of the treated workpieces.

Machines for-automatically moving the dressing 'tool have been proposed, but they are not entirely satisfactory for several reasons: they are expensive; when highiy accurate they involve-a great deal of controlling mechanism and are thus complicated aswell as cumbersome; and, whenmadesirnple and'compac-t, they can not consistently reproduce a particular required wheel surface with any accuracy.

Accordingly,- it is anobject of the present invention to provide an automatic dressing attachment for a grinder that is both compact and highly accurate and is, due to its simplicity, relatively inexpensive;

Another object is to provide an automatic dressing unit for a grinder that can readily be incorporated on'many existing grinders. to replace-the previous mechanisms; whereby dressing operations can be improved without the purchase of an entire new grinder with built-in dress ing. apparatus.

Another object is to provide an automatic-dressingunit in which the mechanism for moving the dressing tool can be mounted on most grinders and the power and control unit for this mechanism can be positioned remotely so as to fit into any available space.

A further object is to provide a power and control-unit for dressing v-appa'ratus that can 'easily'b'e interconnected with the controls for the'workpiece' feeding assemblyin' order to lose a minimum amount of time-between the end of the workpiece feedingoperation and-the beginhing' of the dressing operation and, conversely, to start the workpiece feeding operation the instantthe dressing op eration stops.

A still further object of this invention is topr-o'vide" controlsfor a dressingapparatusthat will insure an extrernelyaccurate dressing operation time'after time, by

precisely controlling both the speed and the direction'of and-forth sliding movement of' EEiiented Mar. 5, 1%63 2 non; with reference to' the accompanying. drawings in which like'refer'en'ce characters refer'to'the' same parts throughout the several views, and in which: 7

FIGURE 1 is 'a side elevational View of a grinding wheel'showing' thedresse'r' and'control' un'it's of this invention" positioned thereon;

FIGURE 2 is' a plan view of'the stuu'ctu're looking in the direction'of the line 2 -2 in FIGURE 1;

FIGURE s'is ase'ct'ional view of'the dressing tool adva'noing' means'taken along lin'e3'3 of FIGUREZ;

FIGUREI4' is a sectional view showing the ratchet mechanism for actuating the advancing means taken along line i -40f FIGURE 2;

FIGURES is'aiio'ther sectional'v'iew showin the ratchet' mech'anism and taken along line5-5 of FIGURE 4';

FIGURE 6' isa sectional view showing the means for retra'cting'the dressing tool from the vicinity of the grinding wheel'taken along line 66 of FIGURE 2;

FIGURE 7 is a sectional view showing the guide point in associationwith the guide bar taken along line 7-7 of FIGURE 6;

FIGURE Sis another sectional view of the guide members taken along line 8-'-8'of FiGURE 7;

FIGURE 9isa view taken along the line in FIG- URE 8 showing the relationship of the guide point and the guide bar; and

FIGURE 10 is a view sho'wingin schematic fashion the control'system of this invention.

The disclosed embodiment o'f'this invention comprises a wheel dressing apparatus 16* mounted oh a conventional support 12 Which'also supports a grinding wheel W, a workpiece feeding'rnechanism' 199 and control units 2198', 266" therefor, respectively, seeFiGURE l. A slide base 14 'is adjustably mounted on an inclined face 15 of the support 12 and locked in position thereon bysuitable bolts 18. The inclined face is is at such an angle that the dressing tool D'+which'in this case is' a diamond cutting '[OOl-Will be movable toward and away from the wheel along a radial line A.

The dressing unit it} is constructed to move the dressing tool D toward and away from the peripheral or Working faceWF of the grinding wheel W along the radial line-A illustrated in'FIGURE l, and also back'and' forth across the working face 'WF of thewhe'el (from left to right and return as seen in FIGURE 2). In addition, the dressing 1001 D is advanced a small controlled distance toward the wheel alongtheradial line A prior to each dressing traverse of the tool across the'working face of the wheel.- 7

Back and forth movement of the tool across the work ing face is'guided by means of-a slide bar 20*integral with adjustable-slide base 14 having an undercut dove tail 22 along one side. Slidable along slide bar 2i} is a first carriage-24' of acompound slide rest having a slide groove 26 along'its under surface which mates with slide bar 2001! the'slide base; The first carriage 24 is slidablebackand forth-along the slide base by means of a hydraulic motor 28 comprising a conventional cylinder 30'adjustably secured to the slide base 14, as by locking screws 32; and containin'g'a piston 34 secured to a piston rod 36which is positively fastened at'its'outer' end tothe first carriage 24 by nut 38. Two'hydraulic fiuid connections 4t) and 42 at either end of cylinde'r'dd provide access for oil for reciprocating the piston within the cylinder;

Movement of the dressing'too'l D toward and away from the Working face of the wheel is accomplished by means of' a second carriage 44 slideable, by means f dovetail ways"46,-on the first carriage and at right angles to the direction of sliding movement of. the first carriage;

Suitable lubricating'ports', not shown, allow easy baclc the first carriage 24, and

3 easy to and fro movement of the second carriage 44 on top of the first carriage, thus providing a double or compound sliding action capable of moving the dressing tool D in any direction within a plane parallel to the sliding surface of slide base 14. The second carriage 44 is moved toward and from the wheel face on top of the first carriage by means of a second hydraulic motor 48 comprising a cylinder t) (see FIGURE 6), a piston 52 and a piston rod 54 terminating in an abutment portion 56 secured to the first carriage 24 by means of a housing 58 containing an abutting surface 6%. The cylinder 50 is secured to a block 64 by bolts 62, and block 64 is in turn locked to the second carriage 44- by means of a dovetail cut out 66 which fits over the slide member 46 of the second carriage and is clamped thereto by a gib 68 and a. clamping screw 71 as seen in FlGURE 7. Hydraulic fluid is admitted to cylinder 59 by connections 72 and 74. Thus as fluid motor 43 is extended by oil pressure through connection 72, the second carriage 44 to which cylinder 5'39 is secured is drawn back on the dovetail ways 46, in

- relation to the first carriage 24 against which piston rod 54 abuts.

As the first carriage moves the dressing tool across the working face of the wheel, the dressing tool is prevented from sliding radially toward the wheel on ways 46 by means of a guide bar 76 and a guide point 78. Guide bar 76 is adjustably secured by means of a clamping block 89 and bolts 82 to the slide base 14. Guide bar 76 has a face BF along which a sharpened edge P of guide point 73 rides; this face BF acts as a cam bar and has a contour machined thereon which is the same contour desired to be obtained on the working face W? of the grinding wheel during the dressing operation. The guide point 78 is secured to the second carriage 44 by being inserted in a suitable bore 84 and held there by a set screw 86. Thus as the first carriage 24 is moved by motor 28 across the face WP of the wheel, the dressing tool D is allowed to approach the wheel no closer than is allowed by the second carriage as it slides on ways 46 and as its guide point P follows the face BF of the guide bar secured to the slide base. The point of edge P of the guide point 78 is approximately the same size as the diamond cutting or dressing tool so that the dressing tool will very ac curately reproduce on the wheels working face the same contour BF that has been machined on the guide bar 76.

This invention also provides apparatus for advancing the. dressing tool radially toward the wheel a small distance prior to the dressing movement of the tool across the working face of the wheel. This distance corresponds to the amount of material to be removed from the wheel by the tool during the dressing traverse, not allowing for the very small reduction in wheel diameter from wear caused by the workpieces previously ground. This apparatus for incrementally advancing the dressing too] D in relation to the second carriage 44 is best seen by referring to FIGURES l, 3, 4 and 5. Dressing tool D is mounted (usually by means of a diamond rotating mechanism, not shown) on a slide rod or tool holder 83 slideable within a sleeve 99, which in turn isadjustably clamped within a surrounding housing on second carriage 44 by any suitable clamping means, not shown. Tool holder 88 is thus movable radially toward the wheel in relation to sleeve it? which is, in effect, a portion of the second carriage 44. This movement is accomplished by a screw connection for finely controlling the incremental advance of the dressing tool.

This screw connection comprises, as best seen in FIG- URE 3, a tapped bore 92 in tool holder 88, and a rotatable member 2% having a threaded portion $6 mating wtih threads 92, and being journaled in bearing 98 within a housing 161 Housing 1th! is affixed to sleeve 99 (and thus to the second carriage 44) by slotted portion 102 which is tightly secured by bolts 1114. Member 94 is rotated within the housing 1% by a worm wheel 1% keyed thereon. Worm wheel 1% is rotated by a worm 4 gear 108 keyed on a shaft 110 which is journaled at 112 in housing 1%. Shaft 1113 may be turned to advance the dressing tool (via worm gear 198, worm wheel 1%, screw connection 96, 92, and tool holder 88) toward the grinding wheel by means of a hand crank 114.

However, automatic means is provided for turning shaft 111) so that errors implicit in manual operation will be eliminated during production line use of the invention. This automatic means consists of a ratchet unit within cover 116 which is removable from the housing 1% simply by removing bolt 118 through the hand crank which holds the entire ratchet unit within cover 116 tightly on conical wedge taper portion 121 of shaft 110. When bolt 118 is removed, hand crank 114 can be removed from the square end 122 of a hollow ratchet shaft 124 which contains a wedge taper 126 compatible with the taper on shaft 11%; Also keyed at on ratchet shaft 124 is a circumferential dial member 130 which in dicates the amount of turn of shaft 11% in relation to markings (not shown) on face 132 of cover 116. When the unit is assembled, tightening bolt 118 renders crank 114, ratchet shaft 124, and worm shaft 110 a unitary structure, as seen in FiGURE 5. This unitary structure is automatically rotatable by a pawl 134 which will rotate a ratchet 136 on ratchet shaft 124 in one direction only. Pawl 134 is oscillated around rotary ratchet 136 by a member 138 which surrounds ratchet shaft 124 and is rotatably separated therefrom by annular bronze bearing sleeve 140.

Member 138 has two ears 142, 144 to which the pawl 134 and its spring 146 for urging the pawl into engagement with the ratchet are attached, respectively. As mem her 133 and its two cars 142, 144 are rotated clockwise (FIGURE 4), pawl 134 will engage the teeth of ratchet and rotate it and the ratchet shaft 124 clockwise; this motion will, due to wedge taper connection 120, 126 (FlGURE 5) thus rotate worm gear shaft 110. Return oscillation of member 138 will not rotate Worm gear shaft 111) back in the opposite direction because the pawl will ride over the inclined side of the ratchet teeth against the urging of spring 14s, as is well known.

Member 133 is oscillated around a certain distance, and then back, once prior to each traverse of the dressing tool across the working face of the grinding wheel by a rectilinearly reciprocable hydraulic motor 150. Best viewed in FIGURE 4, member 138 has a third radially extending car 143 by which the member is oscillated as piston 152 of motor 151) reciprocates within cylinder 154. Elongated piston 152 has, intermediate its ends, a cut out portion 156 for receiving the ear 148. Within the cut out portion 156 a pivot pin 158'secured to the piston 152 rides in a slot 160 in the end of car 148. As piston 152 reciprocates by means of hydraulic fluid admitted to the cylinder through connections 162, 164, member 138 will oscillate pawl 134 by the interaction of the pivot pin 158 in the slot 160 in the end of ear 148. 'In order to get a particular oscillation of member 138 and thus an extremely finely controlled rotation of worm gear shaft 110, a manually adjustable limit stop 166 is utilized to limit the stroke of piston 152 within its cylinder 154.

Means enabling worm gear shaft 110 to be rotated backwards by the hand crank against the braking action of the pawl and ratchet mechanism in emergency situatrons is also provided. When piston 152 is in its rest positron it abuts a stop screw 17% at the bottom end of cylinder 154. When this condition obtains, car 148 oscillates member 138 around counterclockwise (FIGURE 4) to a point where edge 172 of pawl 134 engages a fixed pin 174 and the pawl is thus swung out of engagement with the teeth of the ratchet 136. In this condition the ratchet s ineffective and the worm gear shaft 110 can be rotated 111 either direction by the hand crank. As piston 152 is elevated by fluid admitted through connection 162, car 148 will oscillate member 133 clockwise andpa-wl edge,

172 will be moved away from pin 174 allowing the pawl spring 146 to immediately urge the pawl into engagement with the ratchet teeth and turn the ratchet shaft as the piston 152 continues its upward stroke. In FIGURE 5, the position shown is just after the piston has left its rest position, with the pawl just moving into engagement with the ratchet teeth after leaving pin 174.

Thus one up-and-down reciprocation of hydraulic motor 150 will rotate worm gear shaft 110 a pre-set number of degrees in one direction. And rotation of worm-gear 108 will, through worm wheel 1% and screw connection 96, 92 advance dressing tool holder 88 an increment equivalent to the amount of material the diamond tool is intended to remove from the working face of the grinding wheel on its subsequent traverse. This traverse is effected by motor 28 moving the first carriage 24 parallel to the wheel face while the second carriage 44 and its tool holder 88 ride radially toward and from the wheel in response to the guide point P on the second carriage riding along guide bar BF fixed to the grinder support. After this traverse is completed and the working face of the wheel is satisfactorily dressed, motor 48 draws the second carriage and its associated tool holder radially back along ways 46 away from the vicinity of the grinding wheel and holds it there while motor 28 moves the first carriage 24 back (to the left in FIGURE 2) to its rest position. During this return motion the guide point P is backaway from guide bar BF. The motor 48 returns the second carriage to the vicinity of the grinding wheel until guide point P again rests on guide bar BF. At this point the three motors are in their rest positions and the automatic dressing apparatus is in condition to wait while workpieces-are being fed to and treated by the grinding wheel at the other end of the grinding machine. When a certain number of workpieces have been treated, the wheel again needs dressing, and the above operation is repeated.

The three fluid motors which cause the above described movements are powered and controlled from a remotely positionable unit 2% which may be located at any convenient place on or about the grinding machine 12; such as'on a bench 202. This unit is tied in with andcontrolled by a similar unit 206' located at the opposite end of the machine for powering/and controlling-the workpiece feeding apparatus 199. These two power and control units 200, 200 arecarn-driven liquid column-type motion transfer devices, and they are illustrated schematically in FIGURE 10. The unit- 2% for-powering and controlling the workpiece feedm-achine 199' is only fragmentally shown in the lower right hand corner of the figure,ran'd the part-s,.wherein they are similar, are identified by the same reference character with the addition of'aprime markas the parts in'the unit zee ror powering and controlling the dressing-mechanism 10.

The cam-driven liquid column type motion transfer unit 200 is shown in the upper portion of FIGURE 10. It consists simply of a prime mover 2G4 driving a belt 296 which rotates a worm gear shaft 293. Shaft 298 runs through a'hydraulic clutch 219 and has mounted thereon worm gear 212 for rotating a cam shaft 214 by means of a worm wheel 2 16. Fluid for the hydraulic clutch 210 is pumped from reservoir R by a pump P and through a spring loaded, solenoid actuated valve V. Whenthe valve is in'its spring urged rest position (designated by the unhatched rectangle with the single head flow-direction arrow), fluid will be allowed to flow back to the reservoir through line 213 from clutch210, thus disengaging the clutch and stopping cam shaft 214. When the valve V is in its solenoid actuated position (designated by the cross-hatched rectangle with 'the double head- 2530- forpowering and controlling the feed-mechanism 6. 199" contains similar structure'- with; the additionof a three way valvei ZZG-and a hydraulic brake-222 for worm shaft 208'. When the valve 220. isrin'its: spring urged rest position (designatedfby' the-3 unhatched rectangle) fluid will flow? from the reservoir R through pump-P and to the hydraulic'brake 222(double head flow arrow), and willdr'ainback. to the-reservoir. from clutch 210 (single head'fl'ow arrow), thus holding cam shaft 214- against rotation. When:the-1valve'220is;in its solenoid actuated position (designated by-the' cross-hatched rectangle) fluid will drain fr'omzthebrake222'back'through 1ine-224=to the reservoirR' (singlehead'floW arrow), and Will also pass to clutchiltl (double head arrow), thus'releasing. the brake:and-engagingthe clutch simultaneously 'and enablingsh'aft 214" to rotate-in-vresponse to prime mover 2%: The addition o'f the brake in unit ZhiYisto insurestoppingzofcam shaft'214' at-a-precise rotational point so that the feed mechanism'199 which it controlswillbestopped exactly at the end of a'feed cycle.

While such precision is not'required in the dressing apparatus 10- of the preferred embodiment, such precision'could readily be obtained by the inclusion of a similar brake and three-wayvalve in the power'and control unit 200 for the dresser. In the present embodiment, the cam shaft'Z14 'in unit 200 will coast only a small amount after the clutch 210 is disengaged, and well within feas ible'design latitude-for such a unit without requiringthe use of a brake.

Cam shaft 214 has threefluid motor operating cams thereon, one for powering'and controlling each of the motors of the-automatic-dressing unit 10. Cam 250 controls motor for incrementally advancing the tool holder; cam 228 controls; motor 28 for-traversing the dressing tool across the face of 'thewheel; and cam248 controls motor 48 for withdrawing the second carriage and its tool holder radially from the vicinity of the grindingwheel. 7

Each cam has riding on its peripheral workingfacea cam follower 230 which is linked at 232 to a piston 234. Each cam, follower, link and piston is thus-a-pulsator capable of transmitting motion imparted by rises and falls on the cams surface; The piston of each pulsator reciprocates within a fixed cylinder 236and forms therewith a fluid chamber 238 containing oil-under low, superatmospheric pressure. Attached. to each cylinder and communicatingwith-the chamber is; flexible piping, such as 152, also containing'oil under-low pressure. (Since the pulsator unit and piping for each cam are the same structurally, a-description of the one for cam 250 will suffice to describe all.) As the follower 230 follows a rise ,on cam250, the pulsator piston 234will reduce the size of the chamber Z38=and-thus transmit motion through liquid column 162 to fluid motor 150, wherethe motion isreceived b'y and imparted to piston 15-2;

The steeper the rise on the cam, the faster the movement of the motor piston which receives such motion. The ratio between the facear'easof the -puls'ato'r piston (transmitter) and the motorrpistonfieceiver will. further tend .to govern thespeed with which the motor piston moves as well as the length of its stroke. Obviously, by careful design of the cams. and; careful planning of the areas of the two pistons, a very precise powering and controlling of the fluid motors isobtainedr The cam actuated liquid columntype motion transfer units of this invention also incorporate-means forreturning .thepistons to their rest positionst The oilconnection 164atf the otherend of fluid motor 150, for instance,runs to a supply of oil under high pressure, RO.- This preferably ,is a single air loadedaccumulator connected to supply return oil' (R0) to all of th'ernotorsof thedressing apparatus 10. As. the ,pist'on152 of'motor 150'is return toward its rest positionby the pressure of-thereturn oil through connection 164', the liquid column 162,. 238 acts through thepulsator' to urg'e the camfollower230 continually "against the rauin 'surfaee of ca'u'i 2 50: The'cam 7 on the return stroke serves only to control the speed with which motor piston 152 returns toward its rest position under pressure of the return oil from R0.

The head 246 of each pulsator contains a replenishing check valve 249 and a spring loaded relief valve 242. All the replenishing and relief valves are connected to a common oil source or reservoir 244 formed in the housing of unit 2%. Check valves 240 allow flow from the reservoir 244 to the chamber 238, While relief valves 242 allow flow oppositely when the cylinder pressure exceeds a certain value. Thus each of the pair of valves 24%, 242 may be referred to as a balancing valve and serves to balance the volume of fluid in each of the liquid columns. As a pulsator transmits more motion (fluid displacement) to a motor piston than the pistons limit stops permit, oil pressure will build up at the end of a power stroke and overcome the pre-set force of the relief valves spring and excess oil will be diverted to the reservoir 244. As the cam then passes itspeak and presents a falling face, the pressure of the return oil from R will cause the motor piston, via the liquid column and pulsator, to keep the follower urged against the cam. When the motor piston reaches its limit stop in the rest position, the follower continues to be urged against the cam by the falling pressure in the liquid column. As the cam face falls to near its base circle, the motor stroke is completed and the pressure in the liquid column will fall to near the low, superatmospheric pressure of the reservoir 244. Because oil had been lost from the liquid column through the relief valve during the cams rising portion and the pressure in the liquid column will fall below the reservoir pressure, check valve 240 will replenish the liquid column and keep it at reservoir pressure thus still urging the follower against the cam at all times. And as the cam starts to present a rising face as it begins its next revolution, so the process would be repeated.

Thus a cam actuated liquid column type motion transfer unit 296 is provided which has its own balancing valves 246 for relieving excessive pressures and later replenishing oil to the liquid columns. Further, because of the flexible piping interconnecting the power and control unit and the motors which the unit controls, the unit can be located in any convenient place on or adjacent the grinding machine. Thus an arrangement combining the flexibility of fluid motors and the precision and power of cam control is provided in which simplicity and dependability make the arrangement adaptable to most grinding machines.

The units 205) and 200' for powering and controlling the dressing apparatus 16 and the feeding mechanism 199, respectively, are interconnected by means of a commercial electrical counting device 360 for beginning the dressing cycle immediately upon completion of the feeding of a pre-determined number of workpieces, and to stop the dresser and commence work feeding the instant the dressing operation is complete. The counter 3% contains a conventional ratchet actuating solenoid, or count coil, 302 and a clutch reset solenoid, or clutch coil, 304. In addition, the counter contains a switch for making contact between connections 3% while breaking contact between connections 308 in one position, and vice-versa in the other position. Current for powering the circuitry of count coil 392. During this time contacts 398 are open and 3% are closed, providing power for the solenoid on valve 229 and engaging hydraulic clutch 210' and releasing brake 222. When a preset number of revolutions of cam shaft 214 (determined by the type of workpiece,

etc.) have. been recorded in the counter, the counter switch is thrown to the position shown and contacts 3th: are opened and 3% closed. The instant contacts 3% are opened, the brake 222 is applied and the clutch 210 is disengaged, thus stopping cam shaft 214-.

Closing of contacts 308 closes solenoid actuated switch 329 for starting the prime mover 2&4 of the unit 204 and also actuates solenoid operated valve V to engage hydraulic clutch 21%, thus permitting cam shaft 214 to be rotated by prime mover 2&4. Thus irnmediately upon the counter recording a pre-set number of workpiece feeding cycles, the workpiece feeding mechanism is idled and the dressing apparatus is actuated to begin the dressing cycle. As the cam shaft 21 revolves, the cams 250, 228 and 243 cause the fluid motors 15%, 23 and 48 of the dressing apparatus to incrementally advance the diamond, traverse it across the wheels working face, withdraw it radially from the vicinity of the wheel and return it to its starting point in the manner previously described. Because of the nature of the cams in unit 20%), this sequence can easily be changed to fit any desired sequence, and the sequence described with this preferred embodiment is merely exemplary and not exclusive.

When the fluid motors are again in their rest positions after the dressing cycle has been completed, and before cam shaft 214 has completed its revolution, a cam 322 momentarily closes contacts 324 and pulses current through the counters clutch coil 334 which resets the counter and moves the counters switch to break contact at 368 and make contacts 3%. As current stops flowing through contacts 3%, solenoid switch 329 will shut off prime mover 2M and the spring of valve V will'return it to its rest position disengaging hydraulic clutch 210, thus allowing cam shaft 214 to quickly coast to a stop, and the peaked lobe of cam 32?. to pass just beyond the follower. Closing of contacts 3% again starts unit 2% and the workpiece feeding operation is resumed.

Thus a completely automatic and highly accurate dressing device well adapted to the rigors of high production industrial grinding has been disclosed and, while this particular embodiment constitutes a preferred mode of carrying out this invention, many other forms might be adopted Within the scope of the actual invention, which is variously claimed as:

1. Controls for an automatic grinder including workpiece feeding mechanism and wheel dressing apparatus, said controls comprising two separate mechanico-hydraulic motivators of the liquid column motion transfer type including cam actuated pulsators for transmitting motion through liquid columns to piston receivers in fluid motors, one of said units powering and controlling said grinding cycles, a compound slide rest on the support and a wheel dressing tool mounted on the slide rest for manipulation relative to the wheel, fluid motors con nected to manipulate the tool through a wheel dressing cycle, a mechanico-hydraulic motivator of the rotary cam powered and controlled liquid column motion transfer type connected to operate the fluid motors to dress the Wheel, and control means responsive to the completion of a grinding cycle for rendering the motivator operative to power and control a dressing cycle of the tool and also for rendering it inoperative upon completion of a dressing cycle.

3. An automatic Wheel dresser for a grinding machine comprising a support and a grinding wheel mounted for rotation thereon, a compound slide rest on the support, a wheel dressing tool mounted on the slide rest for manipulation relative to the Wheel, a plurality of shiftable piston type fluid motors each comprising a double acting expansible chamber type pulse receiver connected to manipulate the tool, a plurality of shiftable piston type pulsators each comprising a single acting expansible chamber type pulse transmitter, a plurality of liquid columns connected between the pulsators and the motors to transfer transmitter motions to the receivers in one direction, a source of pressurized fluid, means connecting the source with each fluid motor in opposition to the liquid column connection to bias the receivers counter to transmitted motions, a common liquid reservoir, overload relief and check replenishing valves interconnecting each iiquid column and the reservoir to 10 balance the volume of liquid in each column, a plurality of rotary cams connected to operate the pulsators through a predetermined sequence of movements, and common camshaft means connected to drive the cams in unison whereby the tool is manipulated relative to the wheel through a wheel dressing cycle.

References Cited in the tile of this patent UNITED STATES PATENTS 2,660,930 De Vlieg Dec. 1, 1953 2,710,563 Messmer June 14, 1955 2,720,130 Chang Oct. 11, 1955 2,759,304- Silven Aug. 21, 1955 2,861,561 Olsen Nov. 25, 196 1 FOREIGN PATENTS 701,750 Great Britain Dec. 30, 1953 

1. CONTROLS FOR AN AUTOMATIC GRINDER INCLUDING WORKPIECE FEEDING MECHANISM AND WHEEL DRESSING APPARATUS, SAID CONTROLS COMPRISING TWO SEPARATE MECHANICO-HYDRAULIC MOTIVATORS OF THE LIQUID COLUMN MOTION TRANSFER TYPE INCLUDING CAM ACTUATED PULSATORS FOR TRANSMITTING MOTION THROUGH LIQUID COLUMNS TO PISTON RECEIVERS IN FLUID MOTORS, ONE OF SAID UNITS POWERING AND CONTROLLING SAID FEEDING MECHANISM EXCLUSIVELY AND THE OTHER POWERING AND CONTROLLING SAID DRESSING APPARATUS EXCLUSIVELY; A COUNTING DEVICE ASSOCIATED WITH SAID TWO UNITS; SAID COUNTING DEVICE INCLUDING MEANS, OPERATIVE IN RESPONSE TO MEANS IN SAID ONE UNIT, FOR STOPPING SAID ONE UNIT AND STARTING SAID OTHER UNIT, AND FURTHER RESPONSIVE TO MEANS 